Ink printing apparatuses can be used for single-color or multicolor printing of a printing substrate, for example of a single sheet or of a web-shaped printing substrate made of the most varied materials (paper, for example). The design of such ink printing apparatuses is known; see for example EP 0 788 882 B1. Ink printing apparatuses that, for example, operate according to the Drop-on Demand (DoD) principle have as a printing unit a print head or multiple print heads with nozzle units comprising ink channels and activators, wherein the activators—controlled by a printer controller—can excite ink droplets in the direction of the printing substrate, which ink droplets are directed onto the printing substrate in order to apply print dots for a print image there. The activators can generate ink droplets thermally (bubble jet) or piezoelectrically.
The processing of a printing substrate web as a stacked good should be possible in an ink printing apparatus that prints with high print speeds (>=75 m/min). It is thereby to be taken into account that these ink printing apparatuses have a long printing substrate path (transfer-printing zone with multiple print bars, drying routes) that is typical of an inkjet. This applies in particular given processing of stacked goods in a full-color high-capacity inkjet printer.
A method to control a drive for a printing substrate web in a printing apparatus that prints to a pre-folded printing substrate web with marginal perforation is known from EP 1 047 559 B1. The printing substrate web is transported through the printing apparatus via a drive assembly controlled by a print controller. The printer controller receives signals from a sensor that are dependent on the feed of the printing substrate web. For this, a sprocket is provided whose spokes engage in the marginal perforation of the printing substrate web and is entrained by this. Depending on this, the sensor signals are generated from which the feed velocity of the printing substrate web can be calculated. This is compared with a desired velocity and, given deviations, the feed velocity of the printing substrate web is corrected. Upon insertion of a new printing substrate web, this is manually drawn in by the operator up to the drive assembly. A straight edge on which the printing substrate web can be aligned is arranged on a guide surface at the drive assembly. With a drive motor, the printing substrate web is moved until the beginning of a page rests on a marking on the straight edge. The printing substrate web can subsequently be moved through the printing unit with print velocity.
The feeding of a new printing substrate web into the printing apparatus can also take place in that the new printing substrate web is adhered to a printing substrate web that is already threaded into the printing apparatus and is pulled by this through the printing apparatus. In this case, a synchronization (for example at a fold of the printing substrate web) must take place in the printing apparatus with the aid of a synchronization sensor in order to establish the position of the print images on the printing substrate web. Since the synchronization sensor should be situated before the printing unit of the printing apparatus near its intake, this alignment of the printing substrate web must take place in the printing apparatus, thus at a point in the printing apparatus that is difficult to access. It is thereby to be taken into account that the length of a printing substrate web is dependent on the climate conditions in the region of the printing apparatus, is additionally different for different types of printing substrate web, and additionally can change before the insertion of the printing substrate web into the printing apparatus. A change of the length of the printing substrate web should thus be taken into account, meaning that the synchronization (for example at a fold of the printing substrate web) must be corrected in order to achieve a correct print image on the printing substrate web.